1. In a large, heavy pot, heat butter and olive oil and sauté leek and garlic, stirring occasionally, about 5 minutes. Stir in 2 1/2 cups broth, beans, squash, and rosemary. Bring to a boil, reduce heat, and simmer, covered, about 20 minutes, until squash is tender and beans are soft.

2. While soup is cooking, sprinkle baguette slices with Asiago cheese and toast until cheese just melts. Set aside.

3. Scoop 1-1/2 cups soup into a blender and purée until smooth. Add a bit more broth if necessary. Stir back into the pot. Stir in spinach and cook for 3-4 minutes longer, until greens are just wilted. Season with salt and pepper. Serve hot with cheese toasts and additional Asiago cheese, if desired.